Tool for cutting threads



I July 20, 1943. A. F. ROBERTSON TOOL FOR CUTTING THREADS Filed June 29,1942 4 Sheets-Sheet l I NI/ENTOE Arroezvsk 1 1943- A. F. ROBERTSON 79TOOL FOR CUTTING THREADS Filed June 29, 1942 4 Sheets-Sheet 2 A TTOENA-KJuly 20, 1943.

A. F. ROBERTSON 2,324,879

TOOL FOR CUTTING THREADS Filed June 29, 1942 4 Sheets-Sheet 3//v|/EA/Toe: at $41M 5) ArTaeA/EK JulyZO, 1943. A. F. ROBERTSON TOOL FORCUTTING THREADS Filed June 29, 1942 4 Sheets-Sheet 4 M/vEA/roe: 5y afi4mv Arroe/vsx Patented July 20, 1943 2,324,879 TOOL FOR CUTTING THREADSAlexander F. Robertson, South Euclid, Ohio, assignor to The PipeMachinery Company, Cleve land, Ohio, a corporation of Ohio ApplicationJune 29, 1942, Serial No. 448,935

14 Claims.

This invention relates to thread-cutting tools of the type having cutteror chasers which are movably mounted to be retracted in the operation ofth tool and form taper threads.

The invention has for one of its objects the provision of a tool withreceding and/or collapsing chasers which is adapted to cut internaltaper threads of small diameter and which has improved facilities forthe removal and insertion of the cutters.

Anotherobject of the invention is the provision, in a tap of thereceding chaser type, of means for varying the taper of the threads outcharacterized by accuracy of operation, simplicity of construction andgreat ease of adjustment.

A further object of the invention is the provision of a thread-cuttingtap having improved means for supplying liquid lubricant to the chasersand work during the operation of the tool.

Another object of the invention is the provision of a tool in which theabove objects are realized and which is relatively compact, has asymmetrical, clean cut and pleasing form and which'is easily operated,adjusted and serviced.

Other objects, more or less ancillary or incidental to those abovenoted, will be apparent as this description proceeds.

With the stated objects in view, the invention consists in certainconstructions, arrangements and combinations of parts which areexemplified in a preferred embodiment of the invention shown in theaccompanying drawings.

In the drawings,

Fig. 1 is a vertical axial section of a tool which embodies theinvention. 7

Fig. 2 is a fragmentary elevation of the left side of the apparatus asshown in Fig. 1.

Fig.3 is an elevation of the right side of the apparatus as shown inFig. 1 with a portion of the structure shown in section to disclosinternal construction.

Fig. 4 is a fragmentary view corresponding to Fig. 3 but with parts ofthe tool moved into the positions occupied when the cutters are freedfor removal.

Fig. 5 is a horizontal section on the line 55 of Fig. 1.

Fig. 6 is a horizontal section on the line G6 of Fig. 1.

Fig. 7 is a horizontal section on the line 1'l of Fig. 1.

Figs. 8, 9, 10 and 11 are an outside elevation, a vertical section, aninside elevation, and a forward end view, respectively, of one of thecam parts of the tool. v

Fig. 12 is a vertical axial section similar to Fig. 1 but with the partsof the tool in the positions they occupy when the cutters are freed forremoval, and corresponding to the positions of the parts shown in Fig.4.

Fig. 13 is a fragmentary enlarged axial section showing the forward endof the tool body, the cutters and cutter-actuating means.

Fig. 14 is a section on the line l4| 4 of Fig. 13.

Fig. 15 is a section on the line I5-I5 of Fig. 13.

The tool illustrated in the drawings is in a number of respects similarto the tool disclosed in United States Patent 2,265,764, grantedDecember 9, 1941, to which reference may be made for some features ofconstruction there shown and described in greater detail.

The tool embodying the present invention may be arranged eitherhorizontally or verticall but in the preferred form illustrated in thedrawings it is vertically arranged. It comprises a tool body I securedto a motor-driven spindle 2 by means of screws 3. The spindl 2 isrotatably mounted in a spindle housing 4 which is intended to bevertically reciprocated by any suitable lead screw mechanism (notshown). The tool .body I comprises a main part l and a nose or head ldetachably secured to the forward end of the main part l by means ofscrews 5 and key 6.

The tool body is of tubular or hollow construction and the forwardend ofthe nose I is contracted to small diameter and has its bore :I formedwith a plurality of longitudinal grooves I Nose I is also formed withaiplurality of rectangular apertures l aligned with the grooves I, andin each aperture is'slidably fitted a chaser or cutter 1. Within thetool body isdisposed an inner slide structure composed of parts 8, 9 andH). The part 8 is slidably mounted in and guided by the bore i and iforwardly tapered at its forward end and formed with tongues and groovesto cooperate with complementary grooves and tongues formed on the innersides of the chasers l, as is best shown in Figs. 13 and 14. With thiscam connection between the chasers l and the slide member 8, axialmovement of the latter relative to the chasers serves to move thechasers, such movement being inward when the member 8 is drawn rearwardand outward when the member 8 is moved forward.

The slide member 8 is somewhat enlarged at its forward end and hascylindrical surfaces which slidably engage the bore I of the nose l Asindicated by Figs. 13, 14 and 15, the grooves I of nose I accommodatethe outwardly extending cam parts of member 8. The latter member is heldagainst rotation by a key or spline 8 (Figs. 13 and 15).

The hollow slide member 9 has a swivel connection at its forward end tothe rear end of the member 8 and is formed with internal screw threadsto engage the threaded forward end III of the slide member ID. Themember 8 is slidably supported in a Worm wheel I! which is rotatablysupported in the bore of the body I and operatively secured in positionby a snap ring II. A worm I2 is rotatably mounted in the tool body I tocooperate with and turn the worm wheel II, the latter being connected bya spline l3 to rotate the slide member 9.

The slide member I is slidably supported in the axial bore of anabutment member I! whichin turn is axially slidable in the bore of thetool body I, the member I6 being secured by a spline l against rotationrelative to the abut: ment I4.

"on the outer surface of the tool body I is mounted an outer slidestructure which comprises a main sleeve-like member I6 which slidablyengages the tool body, annular members I1 and I? which are secured tothe forward end of member [6 by screws 19 and a frontworkengagingpressure plate 20 which is secured to the annular member I3by screws 2|. Pressure plate 2!! is centrally apertured to accommodatethe front end of the 'nose' I and the chasers 1.

Taper mechanism In the operation of the tool the outer slide structureengages the work to be threaded so that as the tool body is advancedtoward the work the outer slide structure is given a rear ward movementin relation to the tool body. This relative movement is utilized toeffect a corresponding rearward movement of the inner slide structurerelative to the tool body and thus effect a receding movement of thechasers to cut a thread in taper form.

In accordance with the present invention new and improved operativeconnections are provided between the outer and inner. slide structimesas follows. Interposed between the inner and outer slides is a member 22slidably mounted in the tool body for movement transversely of the toolbody on cordal lines (Figs; 1 and'6). The transverse slide 22 isoperatively secuned in position by a plate or block 23 which is attachedto the tool body by screw 24. The slidably mounted member 22 isoperatively connected to the outer slide structure to be moved therebyand is also operatively connected to the inner slide to effect axialmovement thereof during the thread-cutting operation with resultanttapering of the thread formed, the amount of the axial movement of theinner slide relative to the tool body determining the amount of thethread taper. Referring to the first of the said connections, slide 22carries a pin 25 which pro: jects from the side of the tool body andsupports an annular block or shoe 25 arranged to cooperate with a camplate 21 which has its rear end pivotally connected to slide member 16by a specially formed shoulder bolt 28. On its in-. ner side the camplate 21 is formed with 2 Ion-. gitudinally-extending cam groove 21designed to embrace and, when the outer slide is moved endwise of thetool, to move the block 26 and the slide 22 to which the block isattached.

The amount of transverse movement given to the slide 22 by the cam plate21 depends upon the angular adjustment of the cam plate on its pivotalsupport 28. Such angular adjustment is effected and maintained by ablock 29 which is slidably mounted in outer slide member I6 (Figs. 1 and5) and which is actuated by a screw 30 rotatably secured in slide memberl6 by its integral head and a nut 3L, said screw having its threadsoperatively engaging a threaded aperture in the block 29. The block 29is formed on its inner side a projecting pin 29 which operativelyengages a slot 21 formed in the outer side of-the cam plate 21 at theforward end thereof. The head of the screw 30 is formed with a socket toreceive a wrench for rotating the screw to efiect the adjustment of thecam plate 2?. Preferably the screw 38 is formed adjacent its head withseveral depressions or sockets 30 to be engaged by a springpresseddetent 3% (Fig. 3) to hold the screw yieldingly in the adjustedpositions. However, friction may be relied upon to hold the screw inadjusted position, particularly as the block 21 and screw 30 constitutea non-overhauling device for adjusting and holding the cam plate 21. Theadjusting block 28 is provided on its outer face with a reference mark32 designed to cooperate with an adjacent graduated scale 33 formed onthe slide member l6. This scale 33 may, as shown, include charactersindicating different thread tapers which the tool is adapted to formwhen the reference mark of the adjusting nut 29 is moved opposite therespective characters. Thus, as shown in Fig. 3, we have zero taper (orstraight thread) when the cam groove 21 is parallel to the tool axis andvarious other tapers as the forward end of the cam plate 21 is adjustedto the left from the zero position.

The connection, previously referred to, between the member 22 and theinner slide structure comprises a cam member 32 which has a tongue 34T-shaped in cross section slidably engaging a similarly shaped channel22 in the inner side of slide 22. On it inner side the cam member 34 isformed with a cam tongue 34 which is inclined to a plane at right anglesto the axis of the tool and engages a similarly inclined groove or slot10 in the inner slide member 10 (Figsfl and 6). The cam member 34 ismounted to slide in a transverse slot M formed in the abutment ll sothat transverse movement of the cam 34 with the transverse slide 22 willeffect axial movement of the inner slide structure comprising the parts8, 9 and I0 and thus deter-mine inward or outward movement of thecutters 1. From a consideration of the inclinations of the cam groovesin the plate 21 and in the inner slide member II] (with plate 21adjusted as shown in Fig. 3), it will be seen that forward movement of-the tool body I relative to the work and the work-engaging outer slidewill cause a rearward movement of the inner slide in relation to thetool body I. This gradual rearward movement of the inner slide duringthe thread-cutting operation causes a corresponding retraction orreceding of the chasers, with resultant taper of the thread.

Chaser-collapsing mechanism The abutment ll is provided with a rearwardextension in the form of a rod 35 which is threaded at its front end toengage a threaded hole in the rear end of abutment 14 in which it isadjustably secured by the lock nut 36. The rear end of the rod 35carries a collar 31 which is secured by a nut 38 on the threaded rearend of the rod. A helical sp 39 u ounds t e rod front end against acollar "which in turn abuts against a shoulder in the bore of the toolbody I. Thus the spring 39- serves constantly to urge the abutment I4rearward in the bore of the tool body.

- The spring 39 is normally prevented from moving the abutment I4 by aholding device or latch 4| which is slidably mounted in a radial hole inthe tool body I and engages a notch in the abutment I4. The latch 4| issecured against rotation by a pin 4 I which slidably engages a groove inthe tool body I as shown in Fig. 1. The latch 4| is pressed intoengagement with the abutment I4 by a relatively light helical spring 42which surrounds the stem of the latch and abuts against a collar 43which is secured in position by a block 44 that is in turn secured byscr 45 to the tool body I. The latch 4| and the notch of the abutment I4at their front sides are inclined to the axis of the tool so that thepressure of the large spring 39 tends to move the latch 4| outwardagainst the tension of the light spring 42 to a disengaged position.Such movement of the latch 4| is prevented by a keeper bolt 46 which isslidably mounted in a hole drilled in the block 44. A helical spring 41normally presses bolt 46 forward to overlie the end of the latch 4|.Bolt 46 carries a pin 48 which may "be grasped to manually operate thebolt. Pin 48 projects outward through a slot 44 in the block 44 and theengagement of the pin 48 with the forward end of this slot limits theforward move- Automatic disengagement of latch 4| is effected by a rod49 adjustably mounted on the outer slide in line with the bolt 46. Therod 49 is formed with screw threads engaging the threaded hole of ablock 50 which is secured by screws to the outer slide member I6. Thefront end of the rod 49 is formed with a socket to receive a wrenchindicated by dot-and-dash lines at 53, the pressure plate 29 beingapertured to permit entrance of such wrench to efiect adjustment of therod 49. A set screw 52 is provided to secure the rod in adjustedposition. When the rod is suitably adjusted, its rear end is caused tocontact the bolt ,46 as the thread-cutting operation nears its end.Then, as the relative rearward movement of the outer slide continues,the bolt or keeper 46 is moved out of engagement with the latch 4| andthe latter is forced outward to an inoperative position by the force ofthe large coil spring 39 whereupon the said spring effects the rapidretraction of the abutment I4 and such movement of the abutment carrieswith it the, inner slide members I0, 9 and B with resultant inwardcollapse of the chasers I.

Resetting mechanism When the cutters have been collapsed in the mannerexplained at the end of a threading operation, it is necessary to resetthe tool for a succeeding operation by restoring the movable abutment I4to its forward latched-position. The means for accomplishing this willnow b described. A transverse bar 54 is mounted in a transverse aperturein the abutment I4 with the ends of the bar extending radially outwardthrough slots I, I in the wall of the tool body I. A ring 55 is securedto the ends of bar 54 (Fig.

3) by screws 56 and-blocks 51; said blocks having inwardly-extending lug51 Each of these lugs engages the notched rear end of a tension rodor'bar 58 which is square or rectangular in cross sectionan'd slidablyfits a longitudinal slot I in the tool body I. Each of the bars 58 has aa To provide for the movement of the outer slide to efiectresetting ofthe tool, the slide member I6 is fitted with a ring 59 which isinternally threaded to engage external threads on the slide member I6and has one or more wrench sockets '59 to facilitate turning it on saidslide member.

the ring 59. ring 59 and the ring 64 are of greater pitch than Theapparatus is provided'with stop devices to cooperate with ring 59, saiddevices comprising a yoke 69 having slide parts 60 6|] which engage ways6|, 6| carried by a frame partof the apparatus. The yoke 60 is formed atits forward end with a semicircular part 69 which is of the same radiusas the ring 59 and adapted to engage the rear side of said ring, thecooperating faces of the ring and yoke parts being fitted with hardenedwear plates 59 and 69, respectively.

The weight of the yoke 6|) is sustained by the 4 ring 59 and theyoke'moves freely up and down in the ways 6|.with the upward anddownward movement'of the outer slide of the tool. However, the upwardmovement of the yoke 60 is limited by an adjustable stop in the form ofa screw 62 mounted in a lug or bracket 63 carried by the frameof theapparatus, so that when, following the thread-cutting operation, thetool body is retracted, the rearward-movement of the outer slide of thetool is stopped and with it the bars 58, cross bar 54 and abutment I4,with the result that the continued retraction of the tool body effectsthe resetting of the tool.

Facilities for removing chasers The ring 59 is normally secured againstrotation relative to the slide member I6. Said ring has aforwardly-extending flange part 59 which is internally threaded toreceive an externallythreaded ring 64 which is secured against rotationrelative to slide member I6 by a key 65. In turn the ring 59 is normallylocked to the ring 64 by a key 66 secured by a screw 61 to the ring 59.However, the key 66 is slotted so that by loosening the screw 6! the keycan be moved radially outward and disengaged from the ring 64 to permitrelative rotation of said ring and The screw threads connecting thefacilitate removal of the chasers will be explained in connection withthe description to follow of the operation of the tool.

4 spasm Lubricating moans To feed liquid lubricant or coolant to thecutters during the threading operation the forward end of the outerslide member Ii, which is continuous circumferentially, is provided witha channeled ring 68 to which is attached a pipe 69 th ough which theliquid may be fed in well kn wn manner. The ring 68 is clamped in pooltion by the slide ring I! and the slide members l6, I1 and iii areformed with a plurality of sets of passages I6 ll and I8, respectively,the last named passage communicating with an annular channel l8 formedin ring 18 and from this channel I8 the liquid is discharged through oneor more apertures l8 against the cutters. As will be apparent, theliquid-conducting channels and passages are readily formed in therespective parts as described and the delivery of the lubrieating orcooling fluid to the cutters is accomlished with a minimum ofcomplication.

Th numeral designates as an entirety a clamp device for holding the workto be threaded, such work being indicated at W as a pipe couti ng.

Operation In the operation of the tool mechanism already described,power control devices either of the manual type or of the partially orfully automatic type may be employed to effect the starting and stoppingof the rotational movement of the spindle and the advance and retractionat the spindle housing. These control devices have not been shown in thedrawings and need not be described as any suitable forms ofkncrwnomitrol device may be employed in the operattcn of the tool.

In placing the tool in operation it is first adjusted to provide for thespecific taper, length and diameter of thread to be cut. Adjustment forthe taper desired is effected easily and quickly by rotating the screw89 to adjust the cam plate 21 on its pivotal support to the properangular position. Such adjustment requires merely the application of asuitable wrench to the heed of the screw 30, there being no part orparts to be removed or interchanged or disengaged and the entireoperation consisting in the mere rotation of the adjusting screw, theblock 29 and screw 80 constituting a non-overhauling or self-lockingdevice, as previously stated.

Next the diameter of the thread may be fixed by rotation of the worm IIto turn the worm wheel H and effect a forward or rearward adjust'ment ofthe inner slide members 9 and I,

such rotation of the worm being effected Ily insorting a suitable wrenchor tool through an aperture (not shown) in the slide member 48 in themanner described in the aforesaid Patent No. 2,265,764.

Finally, the adjustment for the length of the thread to be cut iseffected by adjusting the threaded rod 49, this adjustment being made bythe use of the wrench 58, the graduation of which in connection with theface of the pressure plate serving to indicate the desired position ofrod 49.

Assuming that the adjustments have been made and that the working partsof the tool are in the positions shown in Fig. 1 with the chasers I intheir expanded positions and both the inner slide and the outer slide intheir forward positions on the tool body with the abatment l4 latched inits forward position in the tool, then upon the rotation and forwardfeeding o! the machine spindle and'the tool body, the chaser-s I and thepressure plate Ill-are brought into engagement with the rear end of thecoupling W, whereupon the forward movement of the outor slide structureis stopped and the continued forward feeding of the tool results in theadvance of the tool body I in relation to the outer slide structure,which is equivalent to {a rearward movement of the outer slide inrelation to the tool body. This movement causes the cam plate IT to movethe slide 22 transversely of the tool body and with it the cam 34. Suchmovement 01 the cam 34 in turn effects a rearward movement of the innerslide members 00, 9 and 9 which in turn effects a correspondinggradually receding movement of the chasers I with a resuit/ant taper ofthe thread formed by th ohascrs.

As the end of the thread-cutting operation is approached, the rod 49 andthe bolt or keeper 49 come into mutual engagement whereupon furtheradvance of the tool body effects a rearward movement of said bolt inrelation to the latch 4| until the bolt 48 is disengaged from the latch4|. Then the force of the spring 39 acting through the abutment I4forces the latch 4| outword to an inoperative position and the abutmentI4 then is moved quickly rearward by the spring II. This movement of theabutment carrios with it the cam 34 and also the inner slide members l0,9 and I so that at the end of the thread-forming operation the cutterssuddenly are fully collapsed. The rapid movement of the inner slide ispermitted by the T-shape tongue and groove connection between the cam 34and the transverse slide 22 and such movement is accomplished withoutdisturbing the operative connection beween the outer and inner slides.

Upon the collapse of the chasers the feed of the machine is reversed bycontrol mechanism actuated by the ring 55, and the tool is retractedaway from the work, the yoke 60 then being carried rearward in itssupporting ways 8| until it engages the stop screw 62 whereupon rearwardmovement of the outer slide of the tool is stopped, and since the outerslide is connected by the rods 59 with the transverse bar 54 andabutment H the latter parts, together with the inner slide members It, 9and 8, are also stopped in their rearward movement. Consequently as therearward movement of the tool body continues the abutment l4 and theinner slide members are given a relative forward movement in the toolbody against the opposing pressure of spring 8! and the abutment I4 isthus restored to its latched position as shown in 'Fig. 1 and thechssers I are again expanded and made ready for a new cutting operation.

The preceding description of the operation has reference to the cuttingof taper threads. When straight threads are to be cut, it is onlynecessary to adjust the cam plate 21 to the zero taper position byrotation of screw 30 adapt the tool for that purpose. That adjustmentbrings the groove 21 of late 21 parallel to the tool axis so that mutualrelative movement of the tool body and outer slide causes no axialmovement of the inner slide relative to the tool body durmg thethread-cutting operation and no gradual receding 01 the chasers iseffected, although at the end of the cutting operation the abutment I4is unlatched and rapidly retracted to effect the rapid collapse of thechasers, as previously described. Thus, by the easily effectedadjustment of com plate 1'! the tool may be quickly converted from anautomatically receding and collapsing tap for the cutting of taperthreads to a collapsing tap for cutting straight threads; and viceversa.

As will readily be understood the chasers can be collapsed at any timedesired by the operator by manual movement of the pin 48 to permitdisengagement of the latch 4|. ,Also it will be apparent that thechasers can be'reset to their expanded position by grasping the ring 55and. forcing it forward relative. to the tool body.

In taps of the receding and/or collapsing chaser type it has beencustomary to slidably mount .the chasers in notches formed in theforward end of the tool body, such notches being closed at their forwardends by a removable ring which holds the chasers against axial movement.This removable ring is usually secured to the tool body by means ofscrews and the annular front wall of the tool body must be thick enoughto aci commda te the shanks of screws of adequate size and strength.This considerationmakes it possible to reduce the nose of the tool bodyin diameter to the extent which is desirable for the cutting of smalldiameter threads. Consequently in the present invention it has beensought to mount the chasers in rectangular apertures formed in the wallof the tool body nose so'that a front securing ring is not required andso that the thickness of thewall of' the nose can be minimized.'I'Iowever, when the chasers are mounted in ,this manner it is notpossible, becauseof their interlocking connection with the forwardmember of the inner slide, to remove them one at a time, as can be doneWhere a front securing ring is employed. Consequently if the tool bodynose is made small in' diameter and the tapered end of the inner slidemember 8 is made correspondingly small in diameter (as it must be), itbecomes impossible to. disengage all of the chasers from the inner slidemember 8 by retracting the latter, because'as themember 8 is movedrearward the inner edges-f the chasers I go into interference with eachother before the tapered end orcone of memberll can befully disengagedfromthechasers. I

Thus the provision of a tap withreceding or collapsing chasers capableofcutting threads ofquite small diameter has heretofore presented aproblem for which there was no satisfactory solution.

According to the present without disconnecting the connectionsbetweenthe inner and outer slides of the tool or in any way interferringwith or disturbing the adiustments of the tool which determine thediameter, length and taper of'the threads out; The structural means foraccomplishing thislresult have already been described and the way in;

which they function willnow be explained.

When it is desired'to remove the chasersfrom thenose of the tool body,thertool-body is retracted until the yoke 60' is brought in'to contactwith the abutment 62 and is thenstopped. The

key 66 is'then disengaged from the ring 64 and the ring 59 is rotated onthe slide member IS in a direction which would cause thering to travelinvention this problem is solved by the provision'of novel means for"moving the inner slide forward in'the tool bodyand for moving the outerslide-rearward on the t rearwardon the said slide member if suchmovement'were not prevented by the yoke 60 and abutment 62. Because ofthe reaction of the yoke 60 on the ring 59 the rotationof the latter onthe slide member l6 causes said slide member to move rearward on thetool body. Simultaneously the rotation of the ring 59 causes thenonrotatable ring 64 to move forward and in such movement the ring 64carries forward with it the bars 58 and-they in turn advance thetransverse bar 54, the abutment l4 and the inner slide members, inrelation to the tool body and against the tension of the spring 39.Thesere spective movements continue until the parts of the tool reachthe relative positions shown in Fig. 12 where the tapered end or cone ofthe in' ner slide member 8 is advanced far enough to fully disengage thechasers I while the outer slide is retracted far enough to fully uncoverthe said chasers and permit' them to be drawn outward from ,theirrespective apertures in the nose of the tool body.

The chasers, being thus disengaged, can be inspected, or ground or,replaced by new ones. Then, with chasers again positioned in nose I, arotation of the ring 59 in a direction opposite to that in which it wasfirst rotated will permit the pressure of spring 39 to return thevarious .tool parts to their normal positions shown in in the mannerdescribed does not in any way interfere with any of the adjustments ofthe tool which establish the diameter, length and taper of the threadformed by the tool. Nor does such removal of the chasers require orinvolve any disassembly of the tool mechanism, other than the removal ofthe chasers themselves. I n

The novel features of the present invention are not only advantageousindividually but also are interrelated in a manner giving them addedvalue, as willbe appreciated by those, familiar with the various fieldsof thread-cutting work.

ume 'work of'cutting straight threads of small diameter. v

While-a preferred embodiment of the invention has been shown anddescribed it will be understood that the apparatus disclosed can bemodified in a variety of ways by the substitution of equivalents withoutdeparting from the invention as defined in the appended claims;

What is claimed is:

v1. In apparatus for cuttinginternal threads comprising a hollow toolbody operatively mounted for axial and rotational movement and having aforward nose or head part; a plurality of chasers slidably mounted forinward and outward movement in the wall of the nose part of the toolbody; an inner slide structure mounted for axial movement in the toolbody and operatively connected to the chasers to effect their inwardmovement when said inner slide moves rearward in the tool body and theiroutward movement when the slide moves in the opposite direction; anouter slide structure mounted for axial movement on the tool body andcompris ing a work-engaging part, whereby said slide structure is movedrearward relativeto the tool body when the tool body is advancedrelative to the work; and means controlled by the movement of the outerslide relative to the tool body for moving the inner slide lengthwise ofthe tool body and correspondingly moving the chasers in their supportingapertures; the combination therewith of actuating devices operativelyassociated with the inner slide and the outer slide for moving theformer forward and the latter rearward to disengage the inner slide fromthe chasers and permit outward removal of the chasers withoutinterference by the work-engaging part of the outer slide.

2. In apparatus for cutting internal taper threads comprising a hollowtool body operatively mounted for axial and rotational movement andhaving a forward nose or head part; a plurality of chasers slidablymounted for inward and outward movement in the wall of the nose part ofthe tool body; an inner slide structure mounted for axial movement inthe tool body and operatively connected to the chasers to cffect theirinward movement when said inner slide moves rearward in the tool bodyand their outward movement when the slide moves in the oppositedirection; an outer slide structure mounted for axial movement on thetool body and comprising a work-engaging part, whereby said slidestructure is moved rearward relative to the tool body when the tool bodyis advanced relative to the work; and operative connections betweentheinner and outer slide structures for transmitting axial movement of theouter slide relative to the tool body to the inner slide to effectmovement of the'latter in the same direction as the movement of theouter slide and in a predetermined ratio thereto, said operativeconnections permitting axial movement of the inner slide in the toolbody without transmission of sucnmovement to the outer slide; thecombination therewith of actuating devices associated with the innerslide and the outer slide and oper able without interrupting saidoperative connections to move the inner slide forward and the outerslide rearward and disengage the inner slide from the chasers and permitoutward removal of the chasers without interference by the workengagingpart of the outer slide.

3.'Apparatus for cutting internal threads as claimed in claim 1 in whichthe means for mov-- ing the inner slide lengthwise of the tool bodycomprises a movably-mounted abutment 'operatively connected to the innerslide, a spring for moving said abutment, a latch for holding theabutment against movement by the spring, and means for disengaging thelatch at'the end of the thread-cutting operation of the tool to efiectrapid movement of the-abutment and collapse of the chasers.

4. Apparatus for cutting internal threads as claimed in claim 1 in whichthe said actuating devices for moving the inner slide forward and theouter side rearward are operable manually.

5. Apparatus for cutting internal threads as claimed in claim 1 in whichthe said actuating: devices for moving the inner slide forward and theouter slide rearward comprise a movable actuating member, an abutmenttherefor. and

operative connections between the actuating member and the outer andinner slides, respectively, for moving the inner slide forward and theouter slide rearward when the actuating member is moved.

6. Apparatus for cutting internal threads as claimed in claim 1 in whichthe said actuating devices for moving the inner slide forward and theouter slide rearward comprise an actuating member. an abutment therefor,and operative connections between the actuating member and the innerand'outer slides comprising a screw thread on the actuating memberconnected to actuate the inner slide and an opposite screw thread ofsmaller pitch on the actuating member connected to actuate the outerslide.

7. Apparatus for cutting internal threads as claimed in claim 1 in whichthe operative connections between the inner and outer slides comprise amovably mounted abutmentd igned to move the inner slide axially withouta a movement of the outer slide and in which the devices for moving theinner slide forward t 3 cuter slide rearward effect such movement of theinner slide by movement of the said movably mounted abutment.

8. Apparatus for cutting internal threads as claimed in claim 1 in whichthe actuating devices for moving the inner slide forward and the outerslide rearwardcomprise an abutment, an annular actuating member arrangedto operatively engage said abutment and having a screw thread engaging amating screw thread on the outer slide and also having an opposite screwthread of greater pitch, a second annular member keyed to move axiallyon the outer slide and having a screw thread mating with the lastmentioned screw thread of the actuating member, and an operativeconnection between the second annular member and the inner slide.

9. Apparatus for cutting internal taper threads as claimed in claim 2 inwhich the operative connections between the inner and outer slidescomprise a movably mounted abutment designed to move the inner slideaxially without axial movement of the outer slide and in which thedevices for moving the inner slide forward and the outer slide rearwardeffect such movement of the inner slide by movement of said" movablymounted abutment, and in which the apparatus comprises a spring formoving the said abutment, a latch for holding the abutment againstmovement by said spring and means for disengaging the latch at the endofthe threadcutting operation of the tool to efiect rapid movement of theabutment and collapse of the chasers.

10. In a tap for forming taper threads comprising a tool body; means,comprising a chaser movably mounted on the tool body, for cutting athread when the tool body and work to be threaded are given relativerotational and axial movements; an outer work-engaging slide operativelymounted for movement on the tool body in the direction of the tool bodyaxis; and means for transmitting relative axial movement of the outerslide and the tool body to the chaser to effect retraction thereofduring the thread-cutting operation, said means comprising an innerslide structure mounted in the tool body for axial movement in relationthereto and operatively connected to the chaser, a transverse slidestructure operatively mounted for movement in the tool body'transverselythereof, cam connections between: the outer slide and the transverseslide;

and cam connections between the transverse slide and the inner slide,the tap being distinguished by the fact that the said cam connectionsbetween the outer slide and the transverse slide comprise a cam memberpivotally mounted on the inner side of the outer slide and formed tooperatively engage a cam part of the transverse slide and actuatingdevices carried by the outer slide for adjusting said cam member on itspivotal mounting to diiierent positions corresponding to difierentthread tapers to be formed by the tap, said adjusting devices actingautomatically to hold the pivoted cam member in adjusted position.

11. A tap for forming taper threads as claimed in claim in which theactuating devices for adjusting the cam member on the outer slideconstitute a non-overhauling device.

12. A tap for forming taper threads as claimed in claim 10 in which theactuating devices for adjusting the cam member on the outer slidecomprise a screw mounted on the outer slide for rotation without endwisemovement and a threaded block operatively engaging the threads of thescrew and mounted to move endwise of the screw when the latter isrotated.

13. A tap for forming taper threads as claimed in claim 10 comprisingmeans associated with the adjusting means of the pivotally mounted camfor visually indicating different adjustments thereof for causing thetool to cut threads of different specific tapers.

14. Ina thread-cutting tap comprising a tool body; thread-formingchasers movably mounted on the front end of the tool body; an innerslide structure supported in the tool body for contracting and expandingthe chasers; and an outer slide structure operatively connected with theinner slide structure to move the latter longitudinally of the tool bodyand comprising a member slidably mounted on the tool body and heldagainst rotation in relation thereto and having a continuous annularportion; the combination therewith of means for supplying lubricating orcooling liquid to the chaser comprising a ring mounted on said annularportion of the outer 'slide so that the latter can turn in the ring whenthe ring is held against rotation, one of the two relatively turningparts being formed with an interior annular channel for'the lubricatingor cooling 1iquid, a liquid supply conduit connected to said ring incommunication with said annular channel, a separately formed ring havingone of its front and rear sides formed with a circumferentiallyextending channel for liquid with a discharge aperture opening radiallyinward and being attached to the front end of said outer slide memberwith its channel in communication with the first mentioned channel, anda centrally apertured work-engaging pressure plate secured to the frontside of the last named ring.

ALEXANDER F. ROBERTSON.

